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Generic Name: Thyroxine sodium (also known as levothyroxine sodium)
Product Name: Eutroxsig

Indication: What Eutroxsig is used for

Eutroxsig is a medication used to treat conditions of the thyroid gland, particularly hypothyroidism, a condition characterised by low levels of thyroid-produced hormones due to reduced hormone production by the thyroid gland.

It is also used in the treatment of some thyroid tumours and thyroiditis, a condition characterised by inflammation of the thyroid gland. Inflammation can arise due to infection or as a result of auto-immune conditions (conditions in which the immune system functions abnormally) characterised by an immune system attack on thyroid gland tissues or hormones.

Action: How Eutroxsig works

The active ingredient in Eutroxsig, thyroxine sodium, is derived from thyroxine, the principal hormone secreted by the thyroid gland. It replaces hormones normally produced by the thyroid gland. Thyroxine sodium acts in a similar way to thyroxine produced in the thyroid. It works to increase an individual’s metabolic rate and regulate the growth of their body’s cells. It also regulates the function of the thyroid gland.

Dose advice: How to use Eutroxsig

Eutroxsig should be taken once daily after fasting for at least three hours. Food should not be consumed for at least an hour after taking Eutroxsig, as food reduces the absorption of Eutroxsig and in doing so will reduce its effectiveness in replacing thyroid hormones.

The tablets should be swallowed with a glass of water. The tablets should be swallowed whole. If possible, tablets should not be cut.

If you miss a dose, take the dose as soon as you remember. However, if you do not remember until your next dose is almost due, skip the missed dose and continue taking the medicine as prescribed by your doctor. Do not take a double-dose to make up for a missed dose.

Taking too much Eutroxsig (an overdose) may cause symptoms of poisoning, including:

  • Restlessness;
  • Vomiting;
  • Flushing;
  • Breathing difficulties;
  • Chest pains;
  • Convulsions;
  • Paralysis.

If you experience any of these symptoms, seek urgent medical advice or visit the hospital emergency department. Stop taking the medicine immediately if you develop a skin rash or any other symptom suggestive of an allergic reaction.

Dose information

The correct dose of Eutroxsig depends on your age, body weight and other characteristics. To avoid overdose, the doctors start with a low dose and gradually increase the dose over several weeks until you achieve the desired concentration of thyroid hormones in your blood. Blood tests are performed to measure the concentration of thyroid hormones before the dose is increased or decreased. It is important to visit your doctor regularly for monitoring and dose adjustments whilst taking Eutroxsig.

Elderly patients and children require a lower dose than adults. Pregnant women typically require a higher dose. The dose may also vary depending on other medications being used. Always take the dose prescribed by your doctor.

Be aware that it may take several weeks for Eutroxsig to start working. You may not begin to notice your symptoms changing for several weeks after the commencement of therapy. Tell your doctor if you do not think Eutroxsig is working properly for you.


Eutroxsig is packaged in blister packs which should be stored in the refrigerator at 2–8°C. Suboptimal storage (either too hot or too cold) may reduce the potency and effectiveness of the drug.

A single blister pack may be stored unrefrigerated at < 25°C for up to 21 days. You may prefer to store the blister pack from which you are currently taking medicine out of the refrigerator. Short periods out of the refrigerator do not affect the medicine; however, unrefrigerated medicine which has not been used within 21 days should be discarded. If the temperature where you store the medicine is likely to pass 25°C at any time, you must store the medicine in the refrigerator.

Heat and dampness can harm Eutroxsig. Do not store unrefrigerated blister packs in the bathroom, in the car, near windows, or in hot or damp areas. The medicine should be kept out of reach of children.

When not to use this medication

Do not use Eutroxsig tablets which have been unrefrigerated for > 21 days. Tablets should be discarded.

Discard tablets if their colour (usually white) has changed, if the medicine has passed its expiry date, or if the packet shows signs of tampering.

Be aware that Eutroxsig may affect your ability to operate machinery or to drive. Do not perform these tasks until you are familiar with the effects of Eutroxsig.

If you have any queries about the correct way to use Eutroxsig, please ask your doctor.


Eutroxsig should not be used under certain conditions. Tell your doctor if you have or have previously had:

  • An allergy to any thyroid hormone;
  • A disorder of the thyroid gland (Hyperthyroidism);
  • A disorder of the adrenal gland; or
  • Heart problems including heart attack.


Special care needs to be taken when using Eutroxsig under certain conditions. Tell your doctor if you:

  • Have any allergies;
  • Are pregnant or intend to become pregnant. Treatment needs to be carefully monitored during pregnancy by checking concentrations of thyroid hormones in the blood. Pregnant women typically require an increased dose of Eutroxsig in the first trimester of pregnancy;
  • Are breastfeeding;
  • Currently have or have previously had any of the following health conditions:
    • A disorder of the thyroid gland (e.g. hyperthyroidism, hypothyroidism);
    • A disorder affecting the adrenal gland (a hormone-secreting gland located near the kidneys);
    • Heart problems, including cardiovascular disorder;
    • High blood pressure;
    • Diabetes;
  • Are taking any other medications, including medicines you buy without a prescription over the counter. Many medications are known to interact with Eutroxsig and may increase or decrease its effectiveness, meaning that the Eutroxsig dose will need to be increased or decreased. Eutroxsig may also influence the effectiveness of other medicines. Medicines known to interact with Eutroxsig include:
    • Blood-thinning medications (anticoagulants), such as warfarin;
    • Medications used to treat depression (antidepressants), including selective serotonin reuptake inhibitors (SSRIs), lithium and tricyclic antidepressants;
    • Medications used to treat HIV and AIDS (antivirals), including ritonavir;
    • Medications used to treat or prevent malaria (antimalarials), including chloroquine and proaguanil;
    • Medications used to treat diabetes, including insulin;
    • Medications used to treat high blood pressure and heart conditions (often referred to as beta-blockers), including propranolol;
    • Medicines used to treat high cholesterol (ion-exchange receptors), including cholestyramine);
    • Medications used to treat inflammation (corticosteroids), including prednisolone and dexamethasone;
    • Oestrogens, including those contained in oral contraceptives and hormone replacement therapy;
    • Androgens, including testosterone used in hormone replacement therapy;
    • Medications used to treat epilepsy (anti-epileptics), including phenytoin and carbamazepine;
    • Medications used to treat heart failure, including digoxin;
    • Iron supplements;
    • Calcium supplements;
    • Antibiotics including rifampicin (used to treat tuberculosis) and ciprofloxacin (used to treat a range of infectious conditions);
    • Soya bean flour, which may be found in infant formula and other foods;
    • Antacids (used to treat heartburn), including aluminium hydroxide, magnesium hydroxide and calcium carbonate;
    • Amiodarone, a medicine used to treat arrhythmia (irregular heartbeat);
    • Medications used to treat inflammation and associated pain (non-steroidal anti-inflammatory drugs), for example in individuals with arthritis.
  • Tell your doctor or dentist that you are using Eutroxsig before you start taking any other medicine or before you have surgery.


Eutroxsig is a Pregnancy Category A medication. It can be safely used by pregnant women. There is some evidence that thyroxine, the active ingredient in Eutroxsig, is passed on to the foetus of a pregnant woman. However, this does not appear to have any adverse effects on the development of the foetus.

If a woman develops problems with thyroid hormone production which require treatment with Eutroxsig whilst she is pregnant, the condition must be regulated rapidly. A pregnant woman may therefore receive a different dose of Eutroxsig than other people.

Women being treated for existing thyroid problems who plan to become pregnant should ensure treatment is instituted and thyroid hormone levels restored before conception. They should continue Eutroxsig therapy throughout the pregnancy and will require regular blood tests to assess concentrations of thyroid hormones in the blood. Pregnant women usually require an increased Eutroxsig dose in early pregnancy, and a reduced dose after childbirth.


Eutroxsig should be used cautiously by women who are breastfeeding. Tell your doctor before starting Eutroxsig treatment if you are breastfeeding or are planning to breastfeed. Your doctor will need to discuss the potential risks and benefits of undergoing therapy whilst breast feeding.


Children can safely use Eutroxsig. However, they may experience temporary hair loss whilst undergoing treatment. Babies require regular monitoring of thyroid hormone levels because their thyroid gland is more sensitive to Eutroxsig tablets.

Schedule of Eutroxsig

Eutroxsig is a Schedule 4 medication.1

Side effects of Eutroxsig

Common side effects

All medicines have side effects. Most commonly the side effects are minor; however, some can be more serious. Usually the benefits of taking a medication outweigh the associated side effects. Your doctor would have considered these side effects before starting you on Eutroxsig.

The side effects of this medicine usually occur when too much is taken. They include:

  • Nervousness;
  • Restlessness;
  • Excitation;
  • Anxiousness;
  • Muscle weakness and cramps;
  • Inability to sleep or disturbed sleep;
  • Unusual movements including tremor;
  • Headache;
  • Poor concentration;
  • Diarrhoea;
  • Vomiting;
  • Heat intolerance;
  • Excessive perspiration;
  • Flushing;
  • Weight loss;
  • Menstrual irregularities;
  • Decreased sex drive;
  • Fever;
  • Shortness of breath;
  • Rapid breathing;
  • Irregular heartbeat;
  • Chest pain;
  • Hair loss;
  • Irritability.

If you experience any of the listed side effects, or any other symptoms that appear abnormal or unusual, please tell your doctor.


  1. Eutroxsig Product Information [online]. St Leonards, NSW: MIMS Online; 5 June 2009 [cited 17 April 2009]. Available from: [URL link]
  2. Eutroxsig Consumer Medical Information [online]. St Leonards, NSW: MIMS Online; May 2009 [cited 17 April 2009]. Available from: [URL link]

For further information talk to your doctor.

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Posted On: 22 July, 2003
Modified On: 23 October, 2012
Reviewed On: 23 October, 2012


Created by: myVMC